CWNA

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Author:
Tjr31
ID:
36077
Filename:
CWNA
Updated:
2010-09-20 17:39:56
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CWNA
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Description:
ch 4
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  1. Active gain
    created by a devices addition of electrical current to the signal (such as the transmitter or an amplifier
  2. Passive gain
    created by a devices shaping of the signal ( such as an antenna)
  3. Beamwidth
    the measure of how broad or narrow the focus of an antenna is, measuring both horizontally and vertically.
  4. Omnidirectional Antenna
    • radiate rf signal in all direction
    • high gain OA vertical signal decreased and horizontal signal incresed
    • used in point to multipoint indoor enviroments
    • connect multiple buildings
    • make usre the gain is high enough to provide coverage
  5. semidirectional antennas
    • signal in a specific direction
    • short to med distance communication
    • can be tilted downward toward area to be covered
    • 3 types
    • patch panel yagi
  6. Patch
    • outdoor point to point communication up to one mile
    • a central device to provide unidirectional coverage from the ap to the client
    • 180 degree of horizontal beamwidth or less
    • prove coverage for long halways
  7. yagi
    • support a vey narrow range of frequencies
    • length of elements vary according to the wavelength of different frequencies
    • used for short to medium distance point to point comunications up to 2 miles
  8. high directional antennas
    • point to point communications
    • network bridging between 2 buildings
    • focused narrow beamwidth
    • highly affected by wind
    • types parabolic dish, grid
  9. paraboilc dish
    small digital satelite antenna
  10. grid antenna
    • similar to barbecue with curves inward
    • the space between depends on the frequency
    • grid attenna in windy enviroments
  11. phase array antennas
    • is multiple attenas that are onnected to a single processor
    • processor feeds individual antennas
    • transmit multiple beamwidths to mult users
    • expensive
  12. sector antennas
    • high gain semidirectional antenna
    • pie shaped coverage pattern
    • installed in middle of area and placked back to back to eachother
    • together provide omnidirectional coverage
  13. Fresnel zone
    • footballshaped area between two p2p antennas
    • no object to encroach more than 40% of fresnel zone
    • 1st zone 0 to 90 degrees out of phase
    • 2nd zone 90 to 270" "
    • 3rd 270 to 450 " "
  14. earth buldge
    • 7 mies an issue
    • tree problems and mountains
  15. antenna polorization
    • is the direction the electric field and is the same as the the physial attitude if the antenna
    • p2p bridge polarization is imporant
  16. antenna diversity
    • helps to mitigate the effects of multipath
    • not used concurrently
  17. multiple input multiple outpath (MIMO)
    • improve signal quality
    • uses multiple antennae concurrently
  18. placement
    • omnidirectional antennas
    • places in the center of the coverage area
    • low gain provide broader vertical coverage
    • high gain much flatter coverage

    • directional
    • know both vertical and horizontal beamwidths
    • if to strong its a security risk
  19. mounting
    aesthetics and security
  20. maintenance
    preventive and diagonistic
  21. voltage standing wave ratio VSWR
    • change to impedandces to an AC signal
    • signal from cables to the antenna
  22. voltage reflection coefficient (rho)
    ratio between voltage of the reflected wave and the voltage of the incdent antenna.
  23. antenna accessories
    cables, connectors, splitters, amplifier, attenuators, lighting arrestors

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